Studies on the role of pharmacophores in drug discovery have continued. Pharmacophores for HIV integrase, cyclo-oxygenase 2, and tyrosine phosphatase have been identified and used to discover new inhibitors for each of these enzymes. The cell membrane has been modeled and the means by which specific biologically active compounds penetrate this membrane has been studied. The relationships between rate of membrane permeation and molecular size, shape and hydrophobicity have b een examined. Algorithms to calculate molecular hydrophobicity, solubility and partition coefficients have been developed. The entire NCI database of 3D structures of 240,000 open compounds has been posted on the World Wide Web and has been accessed by many labs. around the world.